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BIO 200 CHPT. 11
| Question | Answer |
|---|---|
| Resting membrane potential | V sub r; inside is always negative and outside is always positive; -70mV; polarized; sodium & potassium ions are important for RMP |
| Graded potential | signal that results from change in membrane potential; short distances |
| Action potential | signal that results from change in membrane potential; longer distances |
| Hyperpolarization | inhibits AP; membrane potential changes towards negative (goes in a more neg. direction) ex: -70mV>>-80mV |
| Polarized | differences in ion concentration |
| Sodium is always _____ inside and ______ outside | sodium is always LOW inside and HIGHER outside |
| Calcium is always _______ inside and _________ outside | Calcium is always SUPER LOW inside and HIGHER outside |
| Potassium is always ___________ inside and ________ outside | Potassium is always HIGH inside and LOWER outside |
| Two ways to change the RMP from -70mV | change membrane permeability and change ion concentration |
| Changing membrane permeability | any ion (allows ions to cross the membrane that don't normally cross it); changes RMP |
| Changing ion concentration | changes RMP; intracellular or extracellular |
| Depolarization | required for AP; membrane potential changes towards positive (from neg. to pos.); ex: from -70mV>>-60mV |
| What stimulates graded potentials? | hyperpolarization or depolarization |
| For graded potentials, bigger stimulus means... | bigger "graded potential" |
| Graded potentials decrease with... | distance; localized current flow only |
| Afterhyperpolarization | undershoot; final phase (4) of action potential |
| Absolute refractory | VG Na+ channels open; no other stimulus (regardless of size) can trigger more APs |
| Relative refractory | VG Na+ channels closed; VG K+ channels open; VERY LARGE stimulus will trigger an AP |
| Saltatory conduction | transmission of an action potential along a myelinated fiber in which the nerve impulse appears to leap from gap to gap |
| Three parts to chemical synaptic junction | 1) NT binds to NT receptor; 2) Opens NT/channel & negative ions move inside OR positive ions move inside; 3) Resulting graded potential is depolarization is (+) ion and is hyperpolarization if (-) ions |
| For graded potentials, where do ions flow into the cell? | ONLY at the active site (like a channel) |
| Active current of graded potentials | active site |
| Passive current of graded potentials | ions flowing ALONG membrane surfaces (inside & outside) but not across membrane; redistribution of charge |
| Depolarization with graded potentials | depolarization= (-) outside and (+) inside neighboring areas, continues along membrane surface (a reversal from when at rest) |
| Why can the graded potential occur? (3 important membrane properties) | 1) Membrane insulates (no ions flow across, only along) 2) Fluids inside/outside conduct ion flow 3) membrane permeable to K+ (K+ leaks out of cell) |
| K+ leak channels | K+ is always leaving cell via leaky channels so eventually depolarization will slow |
| Excitable cell examples | neurons, skeletal muscle, cardiac muscle, and smooth muscle |
| Where does graded potential occur? | ONLY in dendrites & cell body (axon to cell body and axon to dendrites) |
| Excitable cells have.. | action potential |
| Action potential is a reversal of what? | membrane potential; goes from -70mV>>+30mV which is depolarization |
| Three changes that occur to membrane permeability in action potential | 1) increase in Na+ permeability 2) return to Na+ impermeability 3) increase in K+ permeability |
| What induces the membrane permeability in action potential? | depolarization |
| Phase 1 of Action potentials | Depolarization; open Na+ channels (activation gate) and Na+ flows in; permeability=high Na+/low K+; positive feedback so more channels open; depolarization of axon leads to more VG channels opening |
| Positive feedback in action potentials | means all this spreads along the membrane and more channels can open |
| Phase 2 of action potentials | VG (Na+) close (inactivation gate closes on Na+ channel); permeability=low N+ & K+; more (+) charge builds up on inside and channels close around 0mV |
| Phase 3 of action potentials | Repolarization; VG (K+) open (K+ ions flow out of the cell); permeability=low Na+ and high K+; cell becomes less (+) as K+ leaves |
| Repolarization | approaching resting conditions |
| Phase 4 of action potential | Undershoot; continued K+ outflux; permeability=low Na+ and high K+; VG (K+) respond slowly stay open; resting ionic concentrations return as increase Na+/K+--ATPase activity |
| During an AP, what ion has the highest permeability during the "undershoot" phase? | K+ |
| Major difference between action potentials & graded potentials? | AP=only involves ions (K+ & Na+) flowing into the cell via voltage gated channels and Graded potentials=passive flow of ions ALONG the membrane (except for where they flow in ONLY at the active site) |
| Propagation | the spreading of something into new regions; i.e. how the AP moves along the axon |
| How does AP move along the axon? | neighboring areas become depolarized & more VG Na+ channels open; AP moves along the axon and "self-propagating" continues along axon |
| Why does AP move only in one direction? (two reasons) | - 1) increased density of VG Na+ channels (***main reason) - 2) refractory period of the Na+ channel (inactive) |
| Where does an AP start? | at axon hillock |
| APs are generated by balance between what? | Na+ entering the cell (depolarizing) and K+ leaving the cell (hyperpolarizing) |
| What if you have a SMALL STIMULUS for APs? | only a few VG Na+ channels open & let in small amount of Na+; K+ leaves via leak channels and remains higher than Na+ entering which results in small depolarization below threshold (-55mV) so NO ACTION POTENTIAL OCCURS |
| Threshold for AP to occur? | -55mV |
| What if you have a LARGE STIMULUS for APs? | Many Na+ channels open letting in large amount of Na+ and then K+ leaves in lower amounts than the Na+ entering resulting in a large depolarization that goes above the threshold and ACTION POTENTIAL OCCURS |
| All-or-None concept of AP | stimulus above threshold=AP; stimulus below threshold=NO AP |
| All APs are the same.... | size (strength) |
| How is stimulus strength of APs transmitted? | as frequency (rather than size); number of APs/unit of time; Bigger stimulus means more APs/unit of time |
| What two variables can affect AP conduction velocities? | Axon diameter and myelin sheath |
| Axon diameter effect on AP conduction velocities | Larger diameter, the faster the conduction rate due to smaller resistance to electrical (ion) flow |
| AP conduction velocity | how fast the AP can move along the axon |
| Myelin Sheath effect on AP conduction velocities | insulates axon which reduces charge leakage; myelinated axons allow for EVEN faster conduction compared to unmyelinated axons; leads to saltatory conduction |
| Multiple Sclerosis | autoimmune disease; loss of myelin that often causes slowing movement of the eye, etc. |
| Axondendritic | axon to dendrite synaptic connection |
| Axosomatic | axon to cell body synaptic connection |
| Axoaxonic | axon to axon synaptic connection |
| Dendrosomatic | dendrite to cell body synaptic connection |
| Dendrodendritic | dendrite to dendrite synaptic connection |
| Presynaptic neuron | "sending" impulse towards the synapse |
| Postsynaptic neuron | impulse away from synapse; "receiving" |
| Botox | blocks the release of neurotransmitter acetylcholine from neuromuscular junction so presynaptic cell can’t release the NT to the muscle |
| Excitatory Postsynaptic Potentials (EPSPs) | depolarization in the postsynaptic cell; Na+ & K+ flow thru a single NT receptor channel |
| Inhibitory Postsynaptic Potentials (IPSPs) | K+ and/or Cl- permeability increased--NT receptor channel; Causes hyperpolarization & reduces MP; will not cause an AP at axon (OR) increases the size of the depolarization that you would need to fire an AP |
| Temporal summation | presynaptic neuron releases NT in rapid sequence on a postsynaptic neuron; produces larger depolarization |
| Spatial summation | one than another presynaptic neuron stimulated at the same time; many NT receptors activated at once; larger depolarization (basically, you have two presynaptic neurons stimulated at the same time so you have larger reaction/depolarization) |
| Post-tetanic potentiation | enhancement occurs after repeated stimulation or "tetanic stimulation"; enhancement can continue even after stimulation stopped (termed post-tetanic stimulation) |
| Acetylcholine | helps with muscles; Neuromuscular junction NT (between neurons & muscles); can be excitatory (neuromuscular junctions) or inhibitory (cardiac) |
| Biogenic amines | Catacholamines; serotonin, dopamine, & epinephrine; NT |
| Catacholamines | serotonin, dopamine, & epinephrine; NT |
| Serotonin | catacholamine; NT |
| Dopamine | catacholamine; NT |
| Epinephrine | catacholamine; NT |
| Glutamate | amino acids; NT; depolarization (excitatory); involved in stroke/seizures |
| Gamma-aminobutyric acid (GABA) | amino acid; NT; hyperpolarization (inhibitory) |
| Endorphins | Peptides; NT |
| Substance P | Peptides; NT |
| Ionotropic receptors | channel-linked receptors; for direct action to open an ion channel; rapid response, localized, & brief |
| Metabotropic recptors | G-protein-linked NT receptors; for indirect action via second messenger; slow response, prolonged, & complex |
| Facilitated zone | Subthreshold stimulation; stimulation from other sources can induce AP |
| Discharge zone | closely linked to presynaptic input; likely to reach threshold |
| Divergence (circuits) | Amplification; single sensory receptor; up spinal cord & multiple brain regions at once |
| Convergence (circuits) | opposite of divergence; multiple presynaptic inputs; concentrated effect; increases response; results in multiple stimuli causes the same response |
| Reverberating circuit | signal comes in, but goes around back & forth in a cycle; could drive something like heart beat or breathing; they generate constant cycles/repeating things |
| Parallel circuit | one signal in, but takes multiple pathways to get an output; ex: problem solving; information goes thru multiple circuits at one time, problem solving circuit, etc. so we are capable of putting information through multiple circuits at one time; |
| Parallel processing | inputs into many different pathways (processed simultaneously); one stimulus travels thru multiple pathways & can cause multiple unique response; for higher mental function |
| 5 types of synaptic connections | axondendritic, axosomatic, axoaxonic, dendrosomatic, dendrodendritic |
| Two types of synaptic junctions in PNS | neuromuscular junctions & neuroglandular junctions |
| Neuromuscular junctions | neuron to muscle; synaptic junction of PNS |
| Neuroglandular junctions | neuron to gland cell; synaptic junction of PNS |
| Two classes of synapses | electrical & chemical synapse |
| Electrical synapse | gap junctions (direct, not chemical, cytoplasmic connections; neuron-neuron); very rapid |
| Chemical synapse | most common junction; release & receive chemical signals; slower signal mechanism; via neurotransmitters; |
| Two parts of chemical synapses | axonal terminal & receptor region |
| Axonal terminal | of chemical synapse; transmitting neuron; presynaptic neuron; synaptic vesicles with NT (bags containing NTs) |
| Receptor region | of chemical synapse; receiving; postsynaptic neuron; NT receptors |
| Synaptic cleft | space between pre & post synaptic neurons |
| Presynaptic cell chemical synapse mechanism (2 steps) | Electrical signal at axon terminal --depolarization --opens VG Na+ & Ca2+ channels (*[Ca2+]) 2) NT released by exocytosis --synaptic vesicles fuse w/membrane --Release NT to synaptic cleft |
| Postsynaptic cell chemical synapse mechanism (2 steps) | 3. NT binds to NT receptor (postsynaptic neuron) 4. NT/NT receptor channels open Conformational change - opens Ion current flow changes membrane potential (graded) Excitation or inhibition |
| Higher frequency of APs at the presynaptic cell= | bigger effect in postsynaptic cell; and more NT released |
| How do drugs affect NT release? | Drugs (toxins) block the release of NT from the presynaptic cell Blocks release of the vesicle containing the NT |
| Three ways the chemical synaptic response can be turned off | 1) enzymes can degrade NTs 2) reuptake of NT 3) just gets diluted and diffuse out of synaptic cleft |
| Small stimulus at postsynaptic cell | no AP occurs as K+ flows out (leak channels) and prevents excessive (+) charge inside the cell |
| Large stimulus at postsynaptic cell | EPSPs move down dendritic process/cell body to axon hillock=graded potential; generates an AP down the axon |
| Which type of synaptic junction is faster--chemical or electrical junction? | electrical (gap junction) because it's a direct link |
| EPSPs can "summate" meaning... | add together; multiple EPSPs on a single postsynaptic neuron so you're more likely to reach threshold--induce an AP |
| If you have EPSP+IPSP.... | =lower depolarization (very slight depolarization because they kinda equal each other out) |
| How does the axon hillock integrate all EPSPs and IPSPs? | determines response (threshold or sub-threshold); closer presynaptic terminal is to axon hillock, greater the influence; example of graded potential |
| Repeated activation of a synapse results in... | postsynaptic neuron is more easily stimulated (called synaptic potentiation) |
| Three criteria for NT | 1) present presynaptic terminal & released with stimulation 2) NT applied to postsynaptic neuron produces response (EPSP or IPSP) 3) natural mechanism exists to terminate response |
| Two types of messengers (recently described NTs) | ATP & nitric oxide |
| Direct NT mechanism | bind to receptor and open ion channel (ACh does this) |
| Indirect NT mechanism | bind to receptor, activate G-protein; activate second messenger; activate/deactivate ion channel; (i.e. serotonin) |
| Two zones of neuronal pools | facilitated zone & discharge zone |
| Circuits | pattern of connection of neuronal pools |
| Four types of circuits | divergence, convergence, reverberating, parallel |
| Serial processing | predictable all-or-none manner; a reflex; stimulus goes through one pathway and then has a response in effector organ |
| Order of serial processing | receptor>sensory neuron>CNS integration>motor neuron>effector (muscle) |
| Two types of neuronal processing | Serial processing & parallel processing |
Created by:
amay322